الفهرس 
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Abstract
Avian colibacillosis remains one of the major endemic diseases of severe
economic significance to all poultry producers worldwide and is characterized
by a diverse array of lesions.
The current study aimed to investigate prevalence of concurrent presence of
APEC infection from different forms of colibacillosis in 61 broiler and 11 layer
flocks at Ismailia governorate during 2014 to 2017 depending on isolation,
culture and colony characterization, serotyping, molecular analysis and
phenotypic characterization using PCR assay targeting virulence genes (iss,
iroN, PapC, cvaC, hly and tsh). Antimicrobials susceptibility profile also was
conducted to estimate the prevalence of antibiotic resistance in examined
chicken flocks. Moreover, we studied experimentally the relationship between
number of virulence genes in chosen field isolates (O1, O125) and their
pathogenicity in broiler chicks and a second trial for treatment with antibiotics.
The results of this study are summarized as follows:-
- The clinical and postmortem examination of 72 flocks revealed typical signs of
avian colibacillosis, especially colisepticemia including respiratory troubles,
greenish diarrhea, fibrinous perihepatitis, pericarditis and airsaculitis.
- A total of 518 tissue samples from different organs (liver, heart, lung, air sac,
unasbsorbed yolk, spleen and oviduct) and cloacal swabs revealed high E. coli
isolation from 246 broilers ( 67.76%) and from 104 layers (67.09%), in which
higher recovery rate of E. coli was from 1iver and heart with a percentage of
(23.14% and 20.33% respectively). Chicks aged (2 to 4 weeks) were the most
affected birds to infections with E. coli.